Accelerator mechanism



March 29, 1966 Filed 001:. 26, 1964 F. P. REED 3,242,816

4 Sheets-Sheet 1 20 4O 12 as 36 FrEElETi ck BREE &

M m x ATf'bRNEYs March 29, 1966 F. P. REED ACCELERATOR MECHANISM 4 Sheets-Sheet 2 Filed Oct. 26, 1964 l EIE |EI INVENTQR FIEHETI'BkEREEfl.

82 7 *7 mw w ATTORNEYS March 29, 1966 REED 3,242,816

ACCELERATOR MECHANISM Filed Oct. 26, 1964 4 Sheets-Sheet 5 INVENTOR FIEflETiBkEREEEL ATTORNEYS March 29, 1966 F. P. REED ACCELERATOR MECHANISM 4 Sheets-Sheet 4 Filed Oct. 26, 1964 TON d f E E S EM M Ek to v c w mfi A E 1U mv F 2 United States Patent Ofifice 3,242,816 Patented Mar. 29, 1966 3,242,816 ACQELERA'EGR MEEHANISM Frederick P. Reed, Ludlow, Mesa, assignor to the United States of America as represented by the Secretary of the Army Filed st. 26, 1964, Ser. No. 4%,627 Claims. (Q1. 89-190) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to automatic guns in which a slide is utilized to actuate a bolt in recoil and counterrecoil and is more particularly directed to means for minimizing the various impacts encountered by the slide and the bolt during the reciprocal travel thereof.

In automatic firearms wherein the recoil and counterrecoil movement of the bolt is imparted thereto by a separate slide, the relatively high velocity required of the slide results in a considerable initial impact with the bolt thereby causing erratic functioning of the recoiling parts as well as a substantial decrease in the endurance life thereof. This is especially true in those designs wherein the bolt is provided with pivotal locks on opposite sides thereof and the slide is formed with longitudinal cam tracks adapted to actuate the locks into and out of locking engagement with the receiver. In this type of bolt and slide structure, any relative movement therebetween during the joint travel thereof in recoil and countenrecoil will actuate the bolt locks into undesirable binding contact with the wall surfaces within the interior of the receiver. Furthermore, since locking of the bolt in battery position is dependent upon the continued closing movement of the slide, it is essential that the latter be prevented firom rebounding upon impact with the receiver at the conclusion of counterrecoil since such reversal of slide movement introduces the dangerous possibility of a partially or fully unlocked bolt at the instant of firing.

Although the prior art has attempted to reduce these impacts of the slide and bolt by suitable buffer means, it is apparent that the addition of springs, guide rods, and other related components creates a relatively complex and unwieldy structure susceptible to erratic function and more frequent malfunction than heretofore. Furthermore, although attempts have been made to reduce the severity of the initial impact between the slide and the bolt through the expedient of a corresponding increase in the compression strength of the recoil springs acting on the slide, it was found that the effectiveness of such approach was nullified by the resulting increase in the impacts encountered by the bolt and the slide at the conclusion of counterrecoil movement.

Accordingly, it is an object of this invention to provide a firearm structure wherein a reciprocating slide is utilized to impart recoil and counterrecoil movement to a bolt without the substantial impacts heretofore encountered at the start and finish of the reciprocal travel thereof.

It is another object of this invention to provide a slide and bolt structure as aforesaid which will include a positive mechanical means for varying the initial velocities of the slide and bolt so as to minimize the magnitude of the subsequent impact therebetween.

A further object of the present invention resides in the provision of .a bolt and slide structure as aforesaid with a mechanical accelerator mounted in the bolt for actuation by the slide such that the bolt will be initially recoiled in a manner which will impart a gradual initial extraction force on the fired cartridge case.

A significant object of this invention is to provide a mechanical accelerator as aforesaid which also reduces the impacts encountered by the bolt and slide at the conclusion of the countcrrecoil movements thereof.

An additional object of this invention is to interpose a mechanical accelerator between a bolt and a slide which will function only during the intervals in which there is relative movement between the slide and bolt.

It is a final object of the present invention to associate a mechanical accelerator with a slide-operated gun bolt in a manner which will improve the endurance life of the recoiling parts and produce greater uniformity in the rate of fire of the gun.

It has been found that the foregoing obiects can be attained by the provision of an L-shaped accelerator pivotally mounted in the underside of a bolt to which recoil movement is imparted by a reciprocating slide. One arm of the accelerator is arranged to depend from the bolt for engagement with a fixed shoulder in the floor of the receiver when the bolt is in battery position while the other arm extends forwardly into the recoil path of an arcuate cam track formed in the rear end of the slide. As the slide recoils to unlock the bolt, this cam track pivots the accelerator in a counterclockwise direction about the point of cont-act with the fixed shoulder in the floor of the receiver in a manner which provides a gradual predetermined acceleration to the bolt such that the velocity thereof will be substantially equivalent to that of the slide when overtaken thereby. Furthermore, as the bolt and the slide approach their respective battery positions during counterrecoil, the impact between the depending arm of the accelerator and the shoulder in the receiver and the subsequent clockwise pivotal movement imparted to the accelerator will produce a substantial decrease in the final velocity of the bolt. In addition, as the accelerator is pivoted by the continuing advance of the bolt, the sliding pressure between the end of the forwardly extending accelerator arm and the arcuate cam track in the rear end of the slide reduces the velocities of both the bolt and the slide. These desirable reductions in the velocities of the bolt and slide during the critical period in which the bolt is being locked to the receiver in battery position, effectively prevents any dangerous rebounding of the slide.

Further objects and advantages of the invention will be apparent from the following specification and the accompanying drawings which are for the purpose of illustration only and in which:

FIG. 1 is a vertical section of the breech portion of a gun in which the present invention may be incorporated and shows the bolt and the slide in the respective battery positions thereof;

FIG. 2 is a section along line 2-2 in FIG. 1 to show the engagement between the bolt locks and the cam tracks in the slide in the locked battery position thereof;

FIG. 3 is a section similar to FIG. 1 but showing the relative positions of the parts immediately after the bolt has been unlocked;

FIG. 4 is a section taken along line 44 in FIG. 3 to show the engagement between the bolt locks and the cam tracks in the slide after the bolt has been unlocked;

FIG. 5 is a section similar to FIGS. 1 and 3 but showing the relative position of the parts as the bolt approaches battery position;

FIG. 6 is a section taken along line 6-5 in FIG. 5 to show the configuration of the slide as seen from the rear;

FIG. 7 is a perspective view of the L-shaped accelerator; and

FIG. 8 is a sectional view taken along line 88 in FIG. 5 to show the manner in which the bolt locks operate to lock the bolt to the receiver.

As illustrated in the drawings, the gun in which the present invention is incorporated includes a receiver 12 having a barrel 14 fixedly mounted in the forward end thereof in axial alignment with a reciprocal bolt 16. A slide 18 is reciprocably mounted in receiver 12 immediately below barrel 14 for recoil movement responsive to a gas piston (not shown) and for counterrecoil movement responsive to a pair of parallel recoil springs Extending forwardly into slide 18 is a central bore 22 beginning with a rearwardly opening counterbored portion 24 of larger diameter. A buffer spring 26, preferably in the form of a ring spring consisting of a series of outer rings 28 surrounding a corresponding series of inner rings 30, is seated in bore 22 under a predetermined initial tension. This is accomplished by a plunger 32 having an enlarged cylindrical head 34 slidab'ly disposed in here 32 for contact with the rear end of buffer spring 26. Plunger head 34 is adjustably retained against rearward movement by a hollow bushing 36 threadably engagea-ble with mating threads 38 in bore 22. Bushing 36 is, in turn, retained in place by an insert 40 having an enlarged head 42 fitting into counterbored portion 24 and a cylindrical body 44 extending forwardly into hollow bushing 36. Insert 40 is centrally drilled, as shown at 46, to provide for the passage of plunger 32 therethrough and is secured in slide 18 by a suitable setscrew 48 as best shown in FIG. 1. The underside of head 42 is semicylindrical while the upper portion thereof is vertiaclly extended by a rectangular block 50 to provide additional height for an arcuate cam surface 52 which extends forwardly and upwardly to terminate at a point spaced rearwardly of the front face of head 42 of insert 40.

Cam surface 52 is utilized to actuate an L-shaped accelerator 54 which is pivotally mounted in a longitudinal slot 56 extending upwardly into the underside of bolt 16 adjacent the rear end thereof. This pivotal mounting is provided by a transverse pin 58 extending through the junction of arms 60 and 62 of accelerator 54 and into bolt 16 on each side of slot 56. As best shown in FIG. 7, arm 69 is of substantially rectangular configuration and extends forwardly to terminate in an enlarged arcuate end 64 adapted for engagement by cam surface 52 during relative movement between slide 18 and bolt 16. Accelerator arm 62 extends downwardly to terminate in a forwardly inclined substantially rectangular end 66 engageable with a fixed vertical shoulder 68 provided in the floor of receiver 12. Arm 62 contains a longitudinal hole 70 therethrough for the passage of the portion of plunger 32 which extends rearwardly from insert 40. As indicated at 72, the portion of bolt 16 containing slot 56 is extended downwardly to provide forwardly facing vertical surfaces adapted for contact by the rear end of slide 18. The rear wall 74 of slot 56 is provided with a hole 76 therethrough substantially equivalent in diameter to hole 70 in accelerator arm 62 and in axial alignment therewith.

The sides of bolt 16 are vertically recessed, as indicated at 78, to receive bolt locks 80 formed with enlarged locking wing portions 82 at the rear end thereof. Each bolt lock 80 is arcuately contoured along the forward edge thereof to rotatably seat in a corresponding groove 84 in the forward wall of bolt recess 78 so that wing portion 82 can be pivoted into and out of locking engagement with a fixed shoulder 86 in the sidewall of receiver 12. The required pivotal movements of bolt locks Si) are imparted therto by suitable cam slots 88 spaced on each side of a central T-slot 91 extending forwardly along the top of slide 18 from the rear end thereof. T-slot 96 engages a mating T-bar portion 92 depending from the underside of bolt 16 while each cam slot 88 slidably receives a diamond-shaped follower 94 depending from the front end of a lateral shelf 96 running along the side of bolt lock 80. Each cam slot 88 includes a linear dwell portion 98 extending forwardly from the rear end of slide 16 and an angular cam portion 1% extending outwardly to intersect the side of slide 18 as best shown in FIG. 2.

As each cartridge 10 2 is fired, the discharge gases actuate a suitable gas piston (not shown) against the front end of slide 18 to impart recoil movement thereto. During the initial recoil movement of slide 18, cam portions 1% actuate followers 94 outwardly and thereby pivot locks 89 about the forward ends thereof so that wing portions 82 thereon are retracted into recesses 78 and out of engagement with fixed shoulders 86 in receiver 12. During the completion of the unlocking of bolt 16, cam surface 53 in the rear end of slide 18 moves into contact with the enlarged forward end 64 of accelerator arm 60 and begins to pivot accelerator 54 about pin 53 thereby advancing accelerator arm 62 into contact with shoulder 5 in the floor of receiver 12.

Thereupon, continued recoil travel of slide 18 will begin to pivot accelerator 54 about shoulder 63 instead of about pivot pin 58. Consequently, due to the mechanical advantage afforded by the length of accelerator arm 62 and the arcuate contour of cam surface 52, bolt 16 will be accelerated from a stationary position to a velocity substantially equivalent to that of slide 18 when overtaken thereby. Thus, as the rear end of slide 13 contacts the forwardly facing surfaces 72 on each side of bolt slot 56, the impact therebetween is virtually eliminated. As bolt 16 is being gradually accelerated, the fired cartridge 102 is correspondingly extracted from the firing chamber in the rear end of barrel 14- without the sudden movement normally encountered in the absence of accelerator 54 as a result of the substantial initial impact between slide 18 and bolt 16.

When the rear end of slide 18 contacts bolt 16, the forward end of accelerator arm 61 will have moved off cam surface 52 and onto the top of slide 18 as best shown in FIG. 3 so that no further pivotal movement is imparted to accelerator 54 during the remainder of the joint recoil travel of bolt 16 and slide 18. As bolt 16 approaches the end of its recoil travel, the projecting end of plunger 32 contacts the rear wall within receiver 12 and compresses buffer spring 26 to reverse the travel of slide 18 before any impact between bolt 16 and the interior of receiver 12. While there may be a slight tendency for slide 13 to separate from bolt 16 at the start of counterrecoil movement, this is effectively prohibited by the sidewalls of receiver 12 which block outward pivotal movement of bolt locks 86.

However, as bolt 16 approaches battery position and end 66 of accelerator arm 62 contacts fixed shoulder 68 in receiver 12, the forward travel of bolt 15 is momentarily delayed relative to slide 18. Thus, as accelerator 54 is pivoted about the point of impact with fixed shoulder 68, the arcu-ate end 64- of arm 60 will be dragged along cam surface 52 to increase the extent to which bolt 16 is decelerated just prior to impact with the breech end of barrel 14. This pressure between accelerator arm 61 and cam surface 52 also reduces the velocity of slide 18 so that the impact thereof in receiver 12 at the conclusion of counterrecoil movement will produce little or no rearward bounce and eliminate the prior art possibility of premature unlocking of bolt 16.

Thus, there is here provided a simple yet positive means for eliminating the undesirable effects of the impacts heretofore encountered upon the transfer of recoil energy from the slide to the bolt and upon the conclusion of the counterrecoil movements of the bolt and of the slide. The concept of pivoting an additional component in the bolt in position to be actuated by a cam surface in the rear end of the slide for imparting a gradual acceleration of the bolt prior to full contact thereof by the slide is considered to provide a unique method for eliminating the former heavy initial impaot therebetween. In addition to the highly desirable manner in which the recoil energy of the slide is transferred to the bolt, the pivotal accelerator of the present invention eliminates undesirable stresses on the extractor and the fired cartridge case at the beginning of extraction. The absence of any significant impact as the slide overtakes the bolt permits a relatively smooth and even travel of these components which results in substantial uniformity of action during successive firing cycles. It is readily apparent that the avoidance of sharp changes in the velocities of the trecoiling parts will provide a higher rate of fire and a substantial increase in the endurance life of the recoiling parts.

The present invention has been described in detail above for the purpose of illustration only and is not intended to be limited by this description or otherwise except as defined by the scope of the appended claims.

I claim:

1. In an automatic gun having a receiver, a bolt slidably disposed in the receiver for reciprocating movement into and out of battery position, and a slide reciprocatingly disposed in the receiver below the bolt for imparting recoil and counterrecoil movement thereto, the improvement of an accelerator having a first arm and a second arm extending integrally from said first arm at substantially right angles thereto, means for pivotally mounting said accelerator Within the bolt with said first arm depending from the underside thereof and said second arm extending forwardly into the recoil path of the slide, and cam means on the slide for pivoting said accelerator to accelerate the bolt to substantially the same velocity as that of the slide at the instant of contact therebetween.

2. The combination defined in claim 1 wherein said cam means on the slide comprises a forwardly and upwardly extending cam surface having an arcuate contour engageable with the end of said second arm of said accelerator during the initial recoil movement of the slide.

3. In an automatic gun having a receiver, a bolt slidably disposed in the receiver for reciprocating movement into and out of battery position, and a slide reciprocatingly disposed in the receiver below the bolt for imparting recoil and counterrecoil movement thereto, the improvement of an accelerator having a first arm and a second arm extending integrally from said first arm at substantially right angles thereto, a transverse pin through the junction of said first and second arms for pivotally mounting said accelerator Within the bolt with said first arm depending from the underside thereof and said second arm extending forwardly into the recoil path of the slide, a vertical shoulder disposed in the floor of the receiver, and a cam surface extending forw ardly and upwardly from the rear end of the slide for contact with said second arm during the initial recoil movement of the slide whereby said accelerator is pivoted about said vertical shoulder in the receiver as a fulcrum to gradually increase the velocity of the bolt in advance of the contact thereof by d the slide so that at the instant of actual contact between both bolt and slide are recoiling at substantially the same velocity.

4. In an automatic gun having a receiver, a slide reciprocatingly disposed in the receiver for recoil and counterrecoil movement, a bolt slidably disposed in the receiver above said slide, said bolt having a depending portion at the rear end thereof extending into the recoil path of said slide whereby corresponding recoil movement is imparted thereby to said bolt, 21 pair of locks pivotally mounted in opposite sides of said bolt for locking engagement with the receiver when said bolt is in battery position, cam track means in said slide for pivoting said bolt looks out of locking engagement with the receiver during the initial recoil movement of said slide, an accelerator having a first arm and a second arm extending integrally from said first arm at right angles thereto, a transverse pin for pivottally mounting said accelerator in said depending portion of said bolt with said first arm extending from the underside thereof and said second arm extending forwardly therefrom into the recoil path of said slide, a vertical shoulder in the receiver positioned immediately in front of said depending arm of said accelerator when said bolt is in battery position, and a cam surface extending forwardly and upwardly from the rear end of said slide in position to contact said second arm of said accelerator duning the initial recoil movement of said slide whereby said accelerator is pivoted about said vertical shoulder in the receiver as a fulcrum to gradually increase the velocity of the bolt in advance of the contact between the rear end of said slide and the front face of said depending portion at the rear end of said bolt so that at the instant of such contact said bolt and slide are both recoil'ing at substantially the same velocity, said accelerator being pivotable about said transverse pin as said first arm thereon moves into contact with said vertical shoulder in the receiver during counterrecoil movement of said bolt into battery position whereby said forward-1y extending second arm bears against said arcwate cam surface on the rear end of said slide to reduce the forward velocity of said bolt and said slide during the locking actuation of said bolt locks.

5. The combination defined in claim 4 wherein said cam track means in said slide include a pair of spaced longitudinal cam slots in the top surface thereof and said bolt locks are each provided with a depend-ing follower at tire forward end thereof slidably engageable in said cam s ots.

No references cited.

BENJAMIN A. BORCHELT, Primary Examiner.

F. C. MATTERN, Assistant Examiner. 

1. IN AN AUTOMATIC GUN HAVING A RECEIVER, A BOLT SLIDABLY DISPOSED IN THE RECEIVER FOR RECIPROCATING MOVEMENT INTO AND OUT OF BATTERY POSITION, AND A SLIDE RECIPROCATINGLY DISPOSED IN THE RECEIVER BELOW THE BOLT FOR IMPARTING RECOIL AND COUNTERRECOIL MOVEMENT THERETO, THE IMPROVEMENT OF AN ACCELERATOR HAVING A FIRST ARM AND A SECOND ARM EXTENDING INTEGRALLY FROM SAID FIRST ARM AT SUBSTANTIALLY RIGHT ANGLES THERETO, MEANS FOR PIVOTALLY MOUNTING SAID ACCELERATOR WITHIN THE BOLT WITH SAID FIRST ARM DEPENDING FROM THE UNDERSIDE THEREOF AND SAID SECOND ARM EXTENDING FORWARDLY INTO THE RECOIL PATH OF THE SLIDE, AND CAM MEANS ON THE SLIDE FOR PIVOTING SAID ACCELERATOR TO ACCELERATE THE BOLT TO SUBSTANTIALLY THE SAME VELOCITY AS THAT OF THE SLIDE AT THE INSTANT OF CONTACT THEREBETWEEN. 